- Which "PH" This Sheet Covers
- The Two-Exam Path at a Glance
- Numbers to Memorize
- Part I Fundamentals: Four Headings
- Part II Surface Water Weights
- Part II Groundwater Weights
- Water Quality: The Verification Hold
- Eligibility Quick Reference
- Fees, Dues and Recertification
- Unresolved Details to Confirm Directly
- Mapping Domains to Study Weeks
- FAQ
- The ordinary PH path is two separate exams: common Part I Fundamentals plus one Part II specialty, Surface Water or Groundwater.
- Surface Water is weighted 31/46/23; Groundwater is 51/38/11. Each specialty totals 100% on its own, so never add across them.
- Passing minimum is 70% per exam, and three failures bar further AIH applications.
- Standard fees total $500 for application plus both exams, before $175 annual dues; recertification is $65 every five years.
Which "PH" This Sheet Covers
On this page, PH means exactly one thing: the Professional Hydrologist credential offered by the American Institute of Hydrology (AIH). It is not a state license, and it is not the HIT (Hydrologic Technician) credential, although the two interact. If you landed here looking for another credential that shares the abbreviation, nothing below applies to it.
If you are still orienting yourself, start with What Is PH Certification? or What Does PH Stand For?. This cheat sheet assumes you already know the credential and want a compact, accurate review of the facts that matter on exam day and in the application process.
The Two-Exam Path at a Glance
The ordinary PH scope is a common Part I (Fundamentals) followed by one applicable Part II specialty. Candidates who already hold a valid HIT credential do not repeat Part I. That is the single most useful fact for early-career people who earned HIT first.
| Item | Part I Fundamentals | Part II Specialty |
|---|---|---|
| Who sits it | Ordinary-path candidates; valid HIT holders skip it | Every candidate, in one chosen specialty |
| Published length | Approximately 100 questions, four hours | 100 questions per Part II detail; introductions say approximate |
| Format | Explicitly multiple choice | Practice examples use multiple choice |
| Passing minimum | 70% | 70% |
| Specialties with published weights | Not applicable | Surface Water; Groundwater |
Combined, the documented path is roughly 200 questions and eight hours, but across two separate exams, not one marathon sitting. Active HIT holders do not owe an additional requirement for this, since they skip Part I.
Numbers to Memorize
- 70%: passing minimum on each exam.
- 3 failures: bars further AIH applications, per the examination page.
- About 100 questions / four hours: published specification per part.
- $100 / $200 / $200: application, Part I and Part II fees.
- $500: calculated initial application-plus-two-exam total, before dues.
- $175: annual PH dues, prorated in the first year.
- $65: five-year recertification fee.
- 3 referees: required with the application.
The pass rate is a number you will not find here. AIH does not disclose an overall PH pass rate, and it does not disclose the scored versus unscored question split. For what the available evidence does and does not say, see PH Pass Rate 2026: What the Data Shows, and for the cut line itself see PH Passing Score 2026: Exactly What You Need to Pass.
Part I Fundamentals: Four Headings
The Fundamentals exam organizes its objectives under four headings. AIH's published allocations are approximately 20/45/30/5 and are approximate question counts, not printed percentages. Treat them as emphasis guidance rather than exact arithmetic.
Domain 1: Water Quantity and Quality in the Field
Field-facing fundamentals: how water is observed, measured and sampled in practice. Roughly 20 questions in the published allocation.
- Know the logic behind field measurement, not only the vocabulary.
- Expect to connect field observations to the quantity-versus-quality distinction.
Domain 2: Quantity and Timing of Flow
The largest Part I heading at roughly 45 questions. This is where hydrology's quantitative core lives.
- Flow magnitude and timing questions reward calculation fluency.
- Open-book and calculator allowances help only if your setup is already organized.
Domain 3: Assessing Water Quality Conditions, Impacts and Sources
Roughly 30 questions on evaluating water quality conditions, their impacts and where problems originate.
- Think diagnosis: what is degraded, why, and from where.
Domain 4: Statistical Analyses
The smallest heading at roughly 5 questions, but statistics underpin interpretation questions elsewhere.
- Small allocation does not mean ignorable; statistical reasoning reappears inside flow and quality problems.
For a deeper walk through how all ten headings relate, see PH Exam Domains 2026: Complete Guide to All 10 Content Areas.
Part II Surface Water Weights
The Surface Water specialty lists three categories, weighted 31%, 46% and 23%. These total 100% on their own.
| Domain | Weight |
|---|---|
| Domain 5: Collection and Inventory of Basic Hydrological Data | 31% |
| Domain 6: Interpretation, Analysis & Modeling of Hydrological Processes | 46% |
| Domain 7: Design Hydrological Systems | 23% |
The takeaway is blunt: nearly half of Surface Water is interpretation, analysis and modeling. A candidate who can collect data but cannot reason about hydrologic processes and models is exposed on the heaviest category.
Part II Groundwater Weights
The Groundwater specialty uses the same three category names, with a very different distribution: 51%, 38% and 11%. Again, these total 100% separately.
| Domain | Weight |
|---|---|
| Domain 8: Collection and Inventory of Basic Hydrological Data | 51% |
| Domain 9: Interpretation, Analysis & Modeling of Hydrological Processes | 38% |
| Domain 10: Design Hydrological Systems | 11% |
Notice the inversion: Surface Water's biggest category is interpretation and modeling (46%), while Groundwater's biggest is collection and inventory (51%). Your choice of specialty changes where the points are, so pick the one that matches your actual professional experience. The same reasoning appears in How Hard Is the PH Exam? Complete Difficulty Guide 2026.
Water Quality: The Verification Hold
AIH's current requirements and bylaws recognize Water Quality as a specialty area. However, a current standalone specialty exam outline or issuer preparation curriculum for it was not verified. So this sheet makes no claim about a Water Quality timer, weighting or exhaustive coverage.
Historical context exists. AIH's examination-development page (with 2023 deadlines) lists question-bank categories for Water Quality: Wastewater; Environmental; Monitoring and Measuring; Limnology; Aquatic chemistry; Microbiology; Soils and sediment; Source pollution and control/treatment; Pollutant fate and transport; and Peripheral Topics. These are development categories, not verified current exam objectives and not a preparation curriculum.
Note that Domains 1 and 3 in Part I do touch water quality at the Fundamentals level. That is separate from the question of a current Water Quality specialty exam.
Eligibility Quick Reference
Current eligibility rests on the AIH Bylaws approved January 30, 2026 (Sections 3.2 and 3.4). The homepage-linked 2026 bylaws control over the still-linked 2024 document. For a fuller treatment, read PH Requirements 2026: Eligibility, Prerequisites & How to Qualify.
| Degree level | Qualifying post-degree hydrology experience |
|---|---|
| Bachelor's | Five years |
| Master's | Four years |
| Doctoral | Three years |
Coursework Requirements
Eligibility coursework is separate from exam content.
- Five semester / eight quarter hours each in chemistry, physics and calculus.
- Three semester / five quarter hours in basic surface-water or groundwater hydrology.
- 25 semester / 40 quarter specialty hours, with at least 10 semester / 16 quarter in Category I and the remainder Category I or II.
- Three referees.
The Approved Coursework List (updated September 14, 2026) supplies eligibility course examples. It is not an exam domain list, so do not study from it as though it were the blueprint. No fixed exam-preparation training hours and no current discretionary waiver thresholds are verified, so do not presume waivers.
Fees, Dues and Recertification
| Item | Standard amount |
|---|---|
| Application | $100 |
| Part I exam | $200 |
| Part II exam | $200 |
| Calculated initial total (before dues) | $500 |
| Annual PH dues | $175, prorated in the first year |
| Five-year recertification | $65 |
Some fine print is worth knowing. The dollar currency is not explicitly labeled USD on the source pages, and no general member versus non-member exam fee pair is published. Organizational-affiliate discounts are conditional.
Candidates weighing the cumulative outlay should read PH Certification Cost 2026: Complete Pricing Breakdown, and those asking whether it pays off can continue to Is the PH Certification Worth It? Complete ROI Analysis 2026 or PH Salary Guide 2026: Complete Earnings Analysis.
Unresolved Details to Confirm Directly
A good cheat sheet admits where the sources conflict. Confirm these with AIH before relying on them.
- Fundamentals timing. The published four-hour Fundamentals specification conflicts with the December 11, 2026 event listing, which shows 9 a.m. to noon. Check the event page and your confirmation email.
- Digital references. The exam is English, open book with references, notes and calculators, and AIH administers it with virtual proctoring. But the reference-computer prohibition versus virtual delivery remains operationally unresolved, so digital-reference permission cannot be inferred. Bring printed or paper materials and ask AIH before test day.
- Continuing development. The requirements page requires at least 12 PDH/PDC annually with documentation each December 31. The continuing-education guidance page describes 60 over five years, submitted by December 31 of year five. Do not treat the five-year guidance as a waiver of the stated annual requirement.
- Vendor. No commercial testing vendor is verified. AIH administers virtual proctoring and Certemy is the application platform.
For scheduling specifics, see PH Exam Dates 2026: Testing Windows, Deadlines & Scheduling.
Mapping Domains to Study Weeks
Because the two exams are separate, sequence them. A sensible plan front-loads whichever exam you will sit first and weights the specialty block by its own distribution. This single timeline is the only generic-method content in this article, and it is tied directly to the weights above.
Part I: Domain 2 first
- Quantity and Timing of Flow is the largest Fundamentals heading, so start there.
- Build your calculation workflow with the calculator you will actually use.
Part I: Domains 1, 3 and 4
- Cover field quantity and quality, quality assessment, and statistics.
- Keep Domain 4 light but present; it supports the others.
Part II: heaviest category first
- Surface Water: lead with Domain 6 interpretation and modeling (46%).
- Groundwater: lead with Domain 8 collection and inventory (51%).
Design and reference organization
- Domain 7 (23%) or Domain 10 (11%) depending on specialty.
- Tab and index your printed open-book references.
The broader preparation picture is in PH Study Guide 2026: How to Pass on Your First Attempt. To pressure-test your recall under realistic conditions, run a set on the PH practice test and review the misses by domain. If your results show a weak category, return to the main practice site and drill that heading specifically.
FAQ
No. Ten counts supported headings across components and alternatives. You sit Part I's four headings plus one Part II specialty's three: either Surface Water or Groundwater.
Valid HIT holders do not repeat Part I. Candidates on the ordinary path take the common Fundamentals exam followed by one Part II specialty.
The passing minimum is 70% on each exam. According to the examination page, three failures bar further AIH applications, so treat each attempt seriously.
AIH recognizes Water Quality in its requirements and bylaws, but a current standalone exam outline or preparation curriculum was not verified. Older development categories exist but are not current exam objectives.
Annual PH dues are $175, prorated in the first year, plus a $65 five-year recertification fee. Continuing-development administration also applies, and the annual and five-year descriptions on AIH's pages conflict, so confirm the current rule with AIH.
For the career side of the credential once you hold it, explore PH Jobs and PH Certification.